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    <title>ShellCheck: SC2244 – Prefer explicit `-n` to check non-empty string (or use `=`/`-ne` to check boolean/integer).</title>
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    <h1>SC2244 – ShellCheck Wiki</h1>
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    <h2
id="prefer-explicit--n-to-check-non-empty-string-or-use--ne-to-check-booleaninteger">Prefer
explicit <code>-n</code> to check non-empty string (or use
<code>=</code>/<code>-ne</code> to check boolean/integer).</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2244.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="cf">if</span> <span class="bu">[</span> <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> <span class="bu">]</span></span>
<span id="cb1-2"><a href="SC2244.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="cf">then</span></span>
<span id="cb1-3"><a href="SC2244.html#cb1-3" aria-hidden="true" tabindex="-1"></a>  <span class="bu">echo</span> <span class="st">&quot;True&quot;</span></span>
<span id="cb1-4"><a href="SC2244.html#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="cf">fi</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2244.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="co"># Check if $1 is empty or non-empty</span></span>
<span id="cb2-2"><a href="SC2244.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="cf">if</span> <span class="bu">[</span> <span class="ot">-n</span> <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> <span class="bu">]</span></span>
<span id="cb2-3"><a href="SC2244.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="cf">then</span></span>
<span id="cb2-4"><a href="SC2244.html#cb2-4" aria-hidden="true" tabindex="-1"></a>  <span class="bu">echo</span> <span class="st">&quot;True, </span><span class="va">$1</span><span class="st"> is a non-empty value&quot;</span></span>
<span id="cb2-5"><a href="SC2244.html#cb2-5" aria-hidden="true" tabindex="-1"></a><span class="cf">fi</span></span>
<span id="cb2-6"><a href="SC2244.html#cb2-6" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb2-7"><a href="SC2244.html#cb2-7" aria-hidden="true" tabindex="-1"></a><span class="co"># Check instead if $1 is true or false, as in Java</span></span>
<span id="cb2-8"><a href="SC2244.html#cb2-8" aria-hidden="true" tabindex="-1"></a><span class="bu">[</span> <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> <span class="ot">=</span> <span class="st">&quot;true&quot;</span> <span class="bu">]</span></span>
<span id="cb2-9"><a href="SC2244.html#cb2-9" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb2-10"><a href="SC2244.html#cb2-10" aria-hidden="true" tabindex="-1"></a><span class="co"># Check instead if $1 is non-zero or zero, as in C</span></span>
<span id="cb2-11"><a href="SC2244.html#cb2-11" aria-hidden="true" tabindex="-1"></a><span class="bu">[</span> <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> <span class="ot">-ne</span> 0 <span class="bu">]</span></span>
<span id="cb2-12"><a href="SC2244.html#cb2-12" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb2-13"><a href="SC2244.html#cb2-13" aria-hidden="true" tabindex="-1"></a><span class="co"># Check instead if $1 is defined (even if just assigned the empty string) or undefined</span></span>
<span id="cb2-14"><a href="SC2244.html#cb2-14" aria-hidden="true" tabindex="-1"></a><span class="bu">[</span> <span class="st">&quot;</span><span class="va">${1</span><span class="op">+</span>x<span class="va">}</span><span class="st">&quot;</span> <span class="ot">=</span> <span class="st">&quot;x&quot;</span> <span class="bu">]</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p><code>[ "$var" ]</code> is equivalent to <code>[ -n "$var" ]</code>
and checks that a string is non-empty.</p>
<p>Users more familiar with other languages are often surprised to learn
that <code>[ "$var" ]</code> is true when:</p>
<ul>
<li><code>var=false</code></li>
<li><code>var=0</code></li>
<li><code>var=null</code></li>
<li><code>var=" "</code></li>
</ul>
<p>Adding the explicit <code>-n</code> helps clarify that this is a
string comparison, and not related to any concept of boolean values or
"truthiness" as it is in most languages.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If you are familiar with the semantics of <code>[</code>, you can <a
href="ignore.html">ignore</a> this stylistic suggestion with no ill
effects.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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